you do know that zebra plecos come literally from the same region as discus right? and again...no heaters ^^
As rude as this sounds, you are really missing a key point here.
I have spent hours with Discus collectors, and spoken with Discus catchers. The water is warm. We over heat them in aquariums, especially when we keep the fancy forms, but the natural water temperatures are from 26-30. I kept my wild caughts at 26, and I've watched wild caught fish breed at 27. Air temperature needs to stay low for quite some time to bring down water temperature, especially with the vast volumes of water in Amazonia. Daytime sun maintains stability.
No heaters for zebra plecos is a trick of the trade. They are found in rushing water - really intense rapids zones. Almost all fish we keep from rapids or fast water have higher oxygen needs. They're adapted to the agitated water conditions, and we are generally incapable of having that much movement. So we cheat - cooler water carries more oxygen. In nature, the highly oxygenated water is warm, above 26. Again, my source is people who have been in the water quite often.
I have one warmish tank with Congo River Cichlids, currently unheated due to summer. It's a 120 US gallon. It has an 800 gph canister, and 2 large Aquaclear HOBS. There is a laminar flow powerhead, a Hydro-Wizard. If I put my hand in I can feel the tug of the water. Oxygen reducers? Go put your ankles in a babbling brook, my friend.
It get an hour of natural sun a day, and even at that, has no algae problems. So I don't get that point.
Over-generalization is a trap we tend to fall into. Stop for a moment, and imagine a Discus trying to live in a roaring current. Then get serious, and look at the sucker mouth of the Loracarid (great for inching along rocks, against a high current) and its habits of getting between rocks with its flattened body. A high bodied Discus built like a sailing ship can handle water that moves many times quicker than anything we have in home aquariums, but a zebra pleco is adapted for life close by a permanantly flusing toilet flow (cleaner water though).
I could take you for a walk around my Canadian home and show you several different habitats with different species assemblages in each, in this small region. Amazonia is vast, and the ecosystem is way more complex than you are presenting.
Btw- I loathe aquarium heaters, which have failed far too many times in my years with tanks. But every fish I keep gets the temperatures reputable collectors have reported them coming from, and I remain aware that when seasons change, so do I.
